The present invention relates to a method and apparatus for driving a magnetic disk and in particular, to a method and means for driving a magnetic disk in a floppy disk unit, which method enables to extend the life of the disk medium and to prevent the read-write head from joining to the surface of the medium.
In a prior art floppy disk unit, two types of methods for driving the disk are known. In one method, a spindle motor is maintained in steady rotation after the power supply is turned on, and the read-write head is loaded on the medium by a head loading mechanism at the time of recording and reproduction. In the other method, the head loading mechanism is not provided, and the read-write head is always maintained in contact with the medium. Further the spindle motor is operated to rotate at the time of recording and reproduction, and the rotation is stopped when finished. In the former, since the spindle motor is kept always rotating, power consumption is undesirably high, whereas in the latter, since the read-write head and the medium are always in contact with each other, wear, demagnetization, adhesion and the like of the medium are caused.
The structure and operation of the former methods will be described with reference to FIGS. 5 and 6.
In FIG. 5, reference numeral 1 designates a recording disk, 2 designates a spindle, 3 designates a door arm, 4 designates a collet, 5 designates a magnetic head, 6 designates a protection case, 7 designates a shaft, 9 designates a solenoid, 10 designates a support pin, and 11 designates an arm.
When the power supply to a floppy disk unit is turned on, rotation operation of the spindle 2 is started, and a steady rotational speed N [rpm] is reached in a fixed time. After that, when a recording medium (the recording disk 1 covered by the protection case 6 is formed in a unit to constitute the recording medium) is inserted into the unit, the spindle 2 and the collect 4 clamp and hold the recording disk 1, and thus the recording disk 1 is driven. Thereafter, at the time of recording and reproduction (read-write), the solenoid 9 is operated by a head loading signal from a floppy disk controller to which the floppy disk unit is connected. When the solenoid 9-which performs raising and lowering operation is operated, by raising one end of the arm 11, the other end of the arm 11 is lowered using the support pin 10 as a support, and the read-write head 5 is brought into contact with the recording disk 1 through an intermediate object, and recording and reproduction operation is carried out.
FIG. 6 is an operating characteristic diagram of the floppy disk unit of FIG. 5.
Upon turning on the power supply to the unit, the spindle motor 6 is started, and the speed increases with the lapse of time and reaches the steady rotational speed N. Thereafter, by inserting the recording medium in the unit, the spindle 2 clamps and holds the recording disk 1. Further, when a magnet of the solenoid 9 is energized by the headloading signal from the floppy disk controller, the magnetic head 5 is moved toward the recording disk 1, and after c seconds from the headloading signal, recording and reproduction operation is carried out. When the recording and reproduction operation is completed, by issuing a HEAD LOAD OFF SIGNAL, the energization of the magnet of the solenoid 9 is shut off, and after the lapse d seconds from the receipt of the HEAD LOAD OFF SIGNAL the magnetic head 5 is completely separated from the recording disk 1 by a return spring.
As regards the latter method, the structure and operation of a floppy disk unit which has no head loading mechanism will be described with reference to FIGS. 7 to 9.
FIGS. 7 and 8 are cross-sectional views of the floppy disk unit in which the recording medium is discharged and is inserted respectively.
In the condition shown in FIG. 7, the recording medium (the recording disk 1 covered by the protection case 6) is inserted, and when the door 3 is closed, the read-write head 5 is brought into contact with the recording disk 1 through an arm 8 connected to the door 3, the recording and reproduction operation is started in the condition of FIG. 8.
The operation in the conditions in FIGS. 7 and 8 is illustrated in FIG. 9.
In the condition of FIG. 7 in which the recording medium is not yet inserted, when a SPINDLE MOTOR ACTUATING SIGNAL is inputted from the floppy disk controller, the spindle motor 2 is actuated, and the rotational speed is increased to the steady rotational speed N [rpm]. Then, when the recording medium is inserted just before the recording and reproduction operation, the condition of FIG. 7 is changed to the condition of FIG. 8, and the recording disk 1 is clamped by the collet 4, and at the same time, the read-write head 5 is brought into contact with the recording disk 1 (head load ON), and the recording and reproduction operation is started. When the recording and reproduction operation is finished, by a spindle motor actuation stopping signal inputted thereto, the rotation of the spindle motor is stopped. In this respect, such unit is described, for example, in Japanese Utility Model Unexamined Publication No. 51-85710 (1976).
As will be apparent from FIG. 9, since the spindle motor is actuated and stopped repeatedly every time the recording and reproduction operation is required, the power consumption can be reduced as compared with the method shown with reference to FIG. 5 in which the spindle motor is always rotating. However, at the same time when the recording medium is inserted, it becomes the head load ON condition and the read-write head 5 is maintained in contact with the recording disk 1. Accordingly, wear and demagnetization of the magnetic surface of the recording medium are further increased, and the life of the recording disk 1 is shortened. Furthermore, when the read or write is not carried out, the recording disk 1 and the read-write head 5 are stopped in a contact with each other. The surface of the disk and that of the head facing are mirror-like surfaces and if such mirror-like surfaces are in contact with each other for a long time, the two surfaces are joined with each other by moisture in the air. If the disk is forced to rotate when the surfaces are joined with each other the magnetic layer of the disk surface is removed, and the data may be destroyed. Further, the recording medium may become unable to be discharged because the two surfaces are joined with each other.
Rapid progress has been made in making the floppy disk units in much smaller size and with larger capacity, and due to this fact, improvement in the reliability of the recording medium and reduction of power consumption of the units are indispensable requirements.
In ordinary floppy disk drives, the rotational speed of the spindle is about 360 r.p.m. to 400 r.p.m. at read/write operation. Two types of methods for inserting the disk into the disk driver are known. In one method, the disk is inserted when the spindle is not rotated. In the other method, the disk is inserted while the spindle rotates. The rotational speed of the spindle at the disk inserting operation is a low speed (e.g. less than 360 r.p.m.) if the operator immediately inserts the floppy disk into the driver just after the spindle is started. However, if the operator inserts the disk after the spindle is started, the rotational speed of the spindle is a steady speed (e.g. 360 r.p.m.). According to the other method, the floppy disk is accurately clamped and held between the spindle and collet because the center of the floppy disk is guided by the rotating spindle and the tapered outer peripheral surface of the collet which are rotating. On the other hand, according to the first mentioned method, the inner edge of the floppy disk may be inserted between the tapered outer peripheral surface of the collet and the tapered circumferential surface of the concave portion in the spindle, and the floppy disk may be deformed.